While the service, held at The Chapel Royal at St. James's Palace, was officially a closed affair, Louis and his proud parents, the Duke and Duchess of Cambridge, made an appearance outside the chapel — as did several other familiar faces.

The former Kate Middleton entered the chapel with the guest of honor in her arms. She wore an off-white dress with long sleeves from Alexander McQueen — the same label she wore for both of her other children's christenings.

The Duchess of Cambridge carries Prince Louis as they arrive for his christening service at the Chapel Royal, St James's Palace, London, Monday, July 9, 2018.Dominic Lipinski / pool via AP

Also in attendance were all six of Louis' new godparents. The Duke and Duchess of Cambridge selected friends and family for the esteemed roles, including Lady Laura Meade (wife of James Meade, Princess Charlotte's godfather), Lucy Middleton (Kate's cousin), Hannah Carter (a longtime friend to Kate), Nicolas van Cutsem (a childhood friend to both William and Prince Harry), Guy Pelly (another childhood pal of the princes) and Harry Aubrey-Fletcher (who also served as usher at the royal nuptials in 2011).

"I’m delighted and privileged to be christening Prince Louis today — a precious child made in God’s image, just as we all are," Welby wrote just hours before the event. "Please join me in praying for him and his family on this special day."